JPH01316768A - Electrophotographic developing device - Google Patents

Abstract

PURPOSE:To enable exact detection of a mixing ratio of a toner and a carrier by providing a collecting member for collecting a developer on the conveying route of the developer using a magnetic roll, and arranging the detection site at the end of the detector of said ratio under the collected developer. CONSTITUTION:The collecting member 10 is arranged on a scraping plate 5 for scraping down the remaining developer on the magnetic roll 4, and the developer flowing along the plate 5 is collected with the member 10, and the detecting site 6A at the end of the detector 6 is arranged under the collected developer, thus permitting the developer to have a sufficient thickness at the detection site 6A, and accordingly, the mixing ratio of the toner and the carrier to be obtained at high precision without causing any detection error.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic developing device.

[Conventional technology]

In developing devices used in electrophotography, a latent charge image formed on a photoreceptor is visualized using a developer that is a mixture of non-magnetic toner and magnetic carrier. It is necessary to keep the mixing ratio approximately constant. For this reason, a method is used in which a toner mixture ratio detector is installed in a developer transport path of a developing device, and the change in the mixture ratio is converted into a change in inductance and detected. Figure 4 shows an example of a conventional developing device.
2 is a developing device, and 2 is an exposed photosensitive drum.

3 is a developer; 4 is a magnetic roll that transports the developer 3 and attaches it to the latent image on the photosensitive drum 2; 5 is a plate for scraping off the developer remaining on the magnetic roll 4 after development; 6 is a toner mixture ratio detector 6A is its detection end.

Reference numeral 7 indicates toner, 8 indicates a toner replenishing device, and 9 indicates a regulation plate for regulating the conveyance amount of the developer 3.

When performing development, the magnetic roll 4 is rotated to convey the developer 3 in the direction of the arrow. At this time, the regulating plate 9 adjusts the UR so that the conveyance amount of the developer 3 is constant. Development is performed by the transported developer 3 adhering to the charged latent image formed on the surface of the photosensitive drum 2.

The developer remaining on the magnetic roll 4 after development is scraped off by the scraper 5, but the scraped developer is deposited on the detection end 6A of the toner mixture ratio detector 6, where the toner and carrier are mixed. The ratio is detected. If it is determined by the detection that the amount of toner is less than the set value, the toner replenishing device 8 is operated to supply the toner 7, and the toner is adjusted so as to always operate at a constant mixing ratio.

[Problems to be Solved by the Invention] As mentioned above, the mixture ratio of toner and carrier is detected by the toner mixture ratio detector each time development is performed, but at this time, the flow rate of the developer flowing through the detection end of the detector depends on the temperature and Since it changes depending on humidity and also due to deterioration, the thickness of the developer deposited on the detection end varies accordingly, which causes a variation in the detected value. FIG. 5 shows the relationship between the developer thickness t and the output As of the toner mixture ratio detector using the inductance variation method when the mixture ratio is constant. Thickness of developer 1) Constant value A s within the range of 1 process
k, but 1. (If it becomes 1□, the value of the output As will decrease and an error will occur.

Therefore, at the time of detection, it is necessary to satisfy 1>1□, but in the conventional method, 1<1□ may occur, which tends to reduce detection accuracy.

An object of the present invention is to provide an electrophotographic developing device that greatly improves the detection accuracy of toner mixture ratio.

[Means to solve the problem]

The present invention provides a magnetic roll that rotates and conveys developer to a photosensitive drum, a toner mixture ratio detector that converts and detects the mixture ratio of non-magnetic toner and magnetic carrier in the developer into a change in inductance, and ! - a toner replenisher that replenishes the toner according to the output of the toner mixture ratio detector;
In an electrophotographic developing device that develops the developer by attaching the developer to the charge latent image formed on the photosensitive drum, a collection member for collecting the developer is provided in a conveyance path of the developer by the magnetic roll; A detection end of the toner mixture ratio detector is disposed on the lower surface of the developer collected by the collecting member, and detection accuracy is improved by increasing the thickness of the R51 developer accumulated at the detection end, thereby achieving the objective. It is calculated by

[Effect]

In an electrophotographic developing device, it is important to maintain a constant mixing ratio of toner and carrier in the developer in order to obtain high-quality images, and this is checked using a toner mixing ratio detector using an inductance variation method. If the thickness of the developer deposited on the detection end of the detector is thin, a detection error will occur.

For this reason, in the developing device of the present invention, for example, a collection member is disposed on a scraping plate that scrapes off the residual developer from the magnetic roll.
The collecting member collects the developer flowing on the scraping plate, and at the same time, the detection end of the detector is placed under the collected developer, so the detection end collects the developer having a sufficient thickness. This makes it possible to detect the mixture ratio of toner and carrier with high precision without causing detection errors.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially enlarged perspective view showing an embodiment of the electrophotographic developing device of the present invention, and FIG. 2 is an explanatory diagram of the developing device in which the mounting position of the detector is different. In both figures, the same reference numerals are used for the same parts as in FIG. 4.

In both figures, 10 is a collection member for collecting the developer 3, and 11 is a collection member for collecting the developer 3.
indicates a frame of the developing device 1.

In FIG. 1, the collection member 10 is provided on the upper part of the scraping plate 5, and in FIG. 2, it is shown attached to the frame 11 below the scraping plate 5.

When the developer 3 flows as shown by dotted arrows in both figures, a part of the developer 3 is collected by the collection member 10 and deposited on the upper part of the detection end 6A. The thickness of the accumulated developer at this time is shown in FIG. 5, and since the thickness is larger than that, no error occurs in the detector 6, and detection can be performed with high accuracy.

FIG. 3 shows a case where the shape of the collection member 10 is an inverted trapezoid,
In this case, the amount collected will be larger than the amount discharged, but the same effect as above can be obtained by combining it with a detector.

〔Effect of the invention〕

As described above, according to the present invention, the following effects can be obtained.

(1) It is possible to provide a developing device that greatly improves the detection accuracy of the mixture ratio of l-toner and carrier. (2) It is possible to obtain high-quality images by improving the detection accuracy of the toner mixture ratio.

[Brief explanation of the drawing]

FIG. 1 shows an electrophotographic developing device of the present invention. FIG. 2 is an explanatory diagram when the detector is attached to a frame; FIG. 3 is a perspective view of a trapezoidal collection member; FIG.
The figure is an explanatory diagram of a conventional device, and FIG. 5 is a characteristic diagram showing the relationship between developer thickness and toner mixture ratio detector output. 1 is a developing device, 2 is a photosensitive drum, 3 is a developer, 4 is a magnetic roll, 6 is a toner mixture ratio detector, and 6A is a detection end. Patent applicant name: Hitachi Eki Co., Ltd.”

Claims (1)

[Scope of Claims] 1. A magnetic roll that conveys the developer to the photosensitive drum through rotational movement, and a toner mixture ratio that converts the mixture ratio of non-magnetic toner and magnetic carrier in the developer into a change in inductance and detects it. An electrophotographic method comprising: a detector; and a toner replenisher for replenishing the toner according to the output of the toner mixture ratio detector; In the developing device, a collection member for collecting the developer is provided on a conveyance path of the developer by the magnetic roll, and a detection end of the toner mixture ratio detector is provided on a lower surface of the developer collected by the collection member. An electrophotographic developing device characterized in that: 2. The electrophotographic developing device according to claim 1, wherein the collecting member collects the developer at a predetermined height. 3. The collection member is disposed on the developer transport path so as to suppress the flow of the developer.
The electrophotographic developing device described in Section 1.